The present invention relates to a rotating electrical machine such as a vertical axis water turbine generator or a horizontal axis large electric motor, and more particularly, to a rotating electrical machine in which fan-shaped segment cores are used in a rotor core.
A rotating electrical machine using fan-shaped segment cores in a rotor core has been proposed as disclosed in, for example, JP-A-5-15093.
Generally, a rotating electrical machine using fan-shaped segment cores in a rotor core includes a rotor core constituted by annular steel plates axially stacked up to a required size, each annular steel plate being formed by circumferentially arranging a plurality of fan-shaped segment cores. In stacking the annular steel plates, ends of segment cores of adjacent annular steel plates in a stacking direction are circumferentially shifted so as not to be aligned with each other.
In the rotating electrical machine including the rotor core constituted by the segment cores, high speed rotation during operation may cause circumferential ends of the segment cores to be displaced radially outwardly as compared with circumferential intermediate portions of the segment cores. Particularly, portions closer to the circumferential ends of the segment cores than fastening bolts passing through the segment cores may be displaced radially outwardly.
This displacement causes slots formed near the circumferential ends of the segment cores to be shifted radially outwardly and circumferentially inwardly with respect to slots formed in circumferential intermediate portions of segment cores of the adjacent annular steel plate in the stacking direction. The shift of the slots cause peripheral edges of the slots near the circumferential ends of the segment cores to protrude into slots of the rotor core formed axially to produce narrow areas in the rotor slots, and rotor windings may abut against the circumferential ends of the segment cores forming the narrow areas to damage insulation of the rotor windings.